That is a problam my brother in law also encountered at the Graffical Lyceum Rotterdam.
(Big school with millions reserve)

It currently is impossible to boot directly to a USB harddisc (flash USB stick will work as well as memeory card Compact flash and the sort, but not a real harddisk.)

So you will have to make a boot floppy / CD.

You can probably use grub to install the bootloader to a floppy but I don't exactly know how he sees a USB harddisk partition.

normally u can use hd (0,x) but for USB I have no idee